Re: [RFC/PATCH] Make powerpc64 use __thread for per-cpu variables

Paul Mackerras
2006-05-10T23:44:39Z

I wrote:

> Hmmm... Would it be sufficient to use a RELOC_HIDE in __get_cpu_var,
> like this?
>
> #define __get_cpu_var(x) (*(RELOC_HIDE(&per_cpu__##x, 0)))

But that won't work because the compiler can still cache &per_cpu__x.
I guess I have to do this:

#define __get_cpu_var(var, cpu) \
(*(__typeof__(&per_cpu__##var))({ \
void *__ptr; \
asm("addi %0,13,per_cpu__"#var"@tprel" \
: "=r" (__ptr)); \
__ptr; \
}))

That means we lose the possible optimization of combining the addi
into a following load or store. Bah. However, I guess it's still
better than what we do at the moment.

Paul.